FIELD DOCUMENTS_1987 - Laserfiche WebLink

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INFORMATION SHEET MARLEY COOLING TOWER CO. STOCKTON, SAN JOAQUIN CO. -2- The Stockton Diverting Canal is an engineered drainage way connecting Upper Mormon Slough to the Calaveras River near the Southern Pacific Railroad crossing. Upper Mormon Slough is actually the South Fork of the Calaveras River below Bellota. From 1 October to 1 April every year, the East Stockton Water District dams the Calaveras River at its fork with Upper Mormon Slough, thus diverting all flows through Upper Mormon Slough and the Stockton Diverting Canal . From 1 April to 1 October every year, flows are split between the Calaveras River and Upper Mormon Slough . A series of check dams are installed along the Calaveras River, Upper Mormon Slough, and the Stockton Diverting Canal to provide irrigation water for adjacent farmers. During this time, there are periods of no flow in the Stockton Diverting Canal . Basis for Effluent Limitations The beneficial uses of the Stockton Diverting Canal are industrial and agri- cultural supply; recreation; esthetic enjoyment; navigation; and preservation of fish and wildlife. These uses are protected by basing effluent limitations on standards to protect aquatic life, human health, agricultural irrigation, and the Regional Board's Basin Plan Objectives. The applicable standards for each of the potential contaminants at MCTC are shown in Table 1. Table 1 standards reflect acceptable levels for instream uses. To determine effluent limits, the most restrictive standard for each constituent was selected . Thus, the respective values used were 6.5 ug/l for Copper, 50 ug/1 for Total Chromium, 11 ug/l for Hexavalent Chromium, 10 ug/1 for Arsenic, and 500 mg/l for Total Dissolved Solids. Since conditions of no flow can exist from 1 April to 1 October, effluent limits for this period were set without considering any dilution. Thus, the limits require effluent quality equal to instream requirements based on the most stringent standard for each constituent above. For 1 October through 1 April , flows in the Stockton Diverting Canal were assumed to be equivalent to releases from New Hogan Reservoir. The lowest daily flowl for the last five years from October to April is 16 cubic feet per second (cfs) . Maximum design flow of the treatment plant is 0.37 mgd, or 0.57 cfs. Thus, in the probable worst case scenario, the dilution factor is 16 to 0.57, or approximately 30:1. Using a safety factor of three, the dilution factor was further reduced to 10:1. Effluent limits were thus set considering a 10:1 dilution factor, using the most stringent standard for each constituent, as discussed above. No limits, however, were allowed to exceed drinking water standards since treatment technology exists and to limit the total mass loadings to the Calaveras River and the Delta. Thus, limits were set at 65 ug/l for Copper, 50 ug/1 for Total Chromium, 50 ug/l for Arsenic, and 500 mg/1 for Total Dissolved Solids . Water-Discharge Records, San Joaquin River Basin, Calaveras River Below New Hogan Dam; U.S. Geologic Survey; 1981-1986 Revised:9/08/87:GAR:gs